In the oldest prior-art systems a feed pipe for a faucet fitting or the like has a threaded end that is covered with dope and threaded tightly into a complementarily threaded bore of the fitting. Such construction requires that threads be formed both in the bore and on the pipe. This is clearly expensive and, if done on the site, time consuming.
Alternately it is known from German patent document 1,650,012 to fit an O-ring around an unthreaded pipe end and force this end into the similarly unthreaded bore. The pipe is held in place by a clamping-nut arrangement. Such a structure is also fairly expensive and complicated, and takes up valuable space, in particular on a fitting adapted to be mounted over a single hole.
German patent document 3,811,357 proposes a structurally simple solution where the tube end is made to an outside diameter that is virtually identical to if not slightly greater than the inside diameter of the bore. The tube end is chilled to shrink it and/or the fitting is heated to expand the bore diameter, and the two are fitted together and cooled, creating a very strong and simple press fit. It is virtually impossible to make such a joint in the field, however, and even at the factory the chilling and/or heating equipment is expensive to run and use.